Green Selective Oxidation of Substituted Indoles Catalyzed by CuCl

An efficient and convenient method for copper-catalyzed green selective oxidative functionalization of indoles using atmospheric O₂ as the terminal oxidant has been developed. This method can be applied to Witkop oxidation and oxidation homocoupling of indoles with good functional group tolerance and substrate scope. Various indoles reacted with molecular oxygen to give the corresponding products in moderate to good yields. A gram-scale experiment can be successfully operated. This protocol provides a sustainable and practical strategy for green oxidation of indoles. By employing this method, multifarious structurally important 2-ketoacetanilide derivatives were efficiently synthesized from simple indoles and complex bioactive molecule derivatives.